What can gas clouds billions of miles away tell us about our origins?
According to a new discovery, at the atomic level, everything. The discovery of two 12 billion-year-old clouds of helium and hydrogen was one of the 10 most important scientific breakthroughs of 2011, according to the journals Science and Physics World.
The discovery, made by UC Santa Cruz Ph.D. student Michele Fumagalli and astrophysicist Dr. J. Xavier Prochaska, confirms that the standard cosmological model, or the way astrophysicists have modeled the creation of the universe and the chemical elements, is correct. Their paper on the discovery, “Detection of Primordial Gas Clouds 2 Billion Years After the Big Bang,” was published in Science last November.
“All we’re doing is counting atoms,” Prochaska said.
What makes these gas cloud atoms unique is that they are composed of helium and hydrogen. The clouds lack “metals,” a term which astrophysicists use to refer to every element besides helium and hydrogen on the periodic table.
Until now, scientists have used two models to study the creation of the universe and elements.
“For almost 50 years, astrophysicists have established two processes for forming the periodic table,” Prochaska said.
The processes Prochaska refers to are Big Bang Nucleosynthesis (BBN) and stellar nucleosynthesis. BBN occurred just after the Big Bang, when everything cooled enough for atoms of only the lightest elements — hydrogen and helium — to form. Over time these light elements formed gas clouds, and eventually stars.
Only then did stellar nucleosynthesis, or the second process begin. Through the heat and pressure created during the life and death of a star, helium and hydrogen underwent fusion, forming almost every other element on the periodic table. When stars died as explosive supernovae, they threw their new metals across space to form everything from planets to life.
While the standard cosmological model is widely accepted, scientists had yet to discover a part of the universe that contained helium and hydrogen but remained unpolluted by metals. Fumagalli and Prochaska’s discovery confirmed that the creation of the elements was derived from two separate processes.
“We had yet to find any part of the universe that had only materials made in the BBN, and none of the stuff that we attribute to stars,” Prochaska said. “It’s the first real confirmation, the cleanest confirmation [of BBN].”
At 12 billion lightyears away, Fumagalli and Prochaska see the clouds as they were 12 billion years ago. Their distance in lightyears corresponds with their age. The universe itself is 14 billion years old, which is more than enough time for metals to have spread throughout space.
Why, then, weren’t these clouds polluted? And what do they say about element distribution throughout the universe? Fumagalli and Prochaska are focusing on these questions in their future work. But to answer them, they will have to find more than two clouds to study — which may prove to be a daunting task.
How common these gas clouds are is unknown, but Prochaska and Fumagalli agree that they can’t be common if this is the first time they have been seen.
“For the most part we suspect that they are not very common,” Fumagalli said. “Perhaps they are not very rare, either.”
Dr. John O’Meara of Saint Michaels College, the third co-author on Fumagalli and Prochaska’s paper, commented in an interview with Popular Mechanics that he hoped these clouds were rare.
“[If] there are a large portion of [unpolluted areas] out there and we just haven’t been finding them, then that means we might have gotten something drastically wrong,” O’Meara said.
Rare or not, the three astrophysicists hadn’t looked for these clouds originally. O’Meara was initially looking at data from gas clouds pertaining to a separate study.
Fumagalli, Prochaska and O’Meara were measuring the absorption of light from distant bright galaxies, known as quasars, by gas clouds. By measuring the light absorbed, the team determined the abundance of different elements in the gas clouds.
It was O’Meara who first saw the results and realized what he was looking at: previously unseen primordial gas clouds. In order to assure that their assessment was accurate, the three began further investigation, leading to one of the biggest scientific breakthroughs of the year.
The honor of being among the top ten scientific breakthroughs of the year in both Science and Physics World came as a surprise. Neither Fumagalli or Prochaska knew they had earned the spot until the magazines were published.
The spot was “unexpected,” said Fumagalli, but it was a “very exciting” surprise.
Fumagalli and Prochaska are currently using their results to work with other astrophysicists using computer simulations to show how the universe and galaxies might form and how gases might be distributed.
“We meet them with our observations,” Prochaska said, “and go from there.”